Checking rotary valve clearances

Rotary valves are precisely machined to accommodate very tight internal clearances. In a smaller standard valve there should be a .003” – .005” gap between the tips and ends of the rotor and the housing / headplate. However, the clearances on many valves are customized to meet the needs of a specific application. For example, in applications with temperature greater than 70°F, the clearances may need to be larger to allow for thermal expansion. Before examining the valve, contact Wm. W. Meyer & Sons to find out what internal clearances your valve was configured with.

It is important to maintain tight clearances; this allows the airlock valve to effectively create a seal, while maintaining a flow of material between components with different pressure. However, just like anything else, rotary valves wear out too. The lifespan of a rotary valve typically depends on the characteristics of the material going through it, the features it was constructed with, the application it is used in, and the amount of preventative maintenance performed. Some valves remain in service for 30+ years without wearing out. Others need to be replaced or rebuilt several times a year. Typically valves operating in abrasive environments have shorter life spans.

There are two main reasons one would need to check the clearances on a rotary valve. Either the valve is making a sound indicative of the rotor coming into contact with the housing, or symptoms of air leaking through the valve are present. However, if a new valve is making a high pitched noise, several things should be done before checking the clearances.

First, check with the supplier of your valve to find out what temperature your equipment was manufactured to accept. If the material going through the airlock is at a higher temperature than the valve was built to handle; checking the clearances will not solve the problem.
Next, make sure the rotary valve is level. The airlock should be bolted to a perfectly flat surface on top and bottom. The slightest amount of torsion could deplete the extremely small internal clearances, causing the rotor to come into contact with the housing or headplate.
Regardless of the reason why the clearances need to be checked, the same procedure should be used. Listed below are step by step instructions, but before getting started, make sure to gather the tools necessary to complete the task.

You Will Need

• Lockout-Tag out Padlock
• Pair of Needle Nose Pliers (or tool for removing chain links)
• Phillips Head Screw Driver
• Set of Feeler Gauges .001 – .015